MP3 Wiring Layout of USB Connection

[Strato]

Hi there,

I have a question regarding the wiring layout depicted here: https://www.goldenmotor.com/e-Bike-DIY/MP3%20SmartPie%20Wiring%20Layout.jpg
Are the cables for Signal Receive and Signal Transmission labeled from the perspective of the PC or the controller? So does Receive mean, the PC receives data and Transmission the PC transmits data or is it the other way round?

Would be glad to get any help.

P.S. I hope it was right to have posted this request as a reply of the new members' introduction post

[Bikemad]

Hi Strato andto the forum.

The Transmit and Receive labels relates to the Transmit and Receive connections on the controller itself, not the USB connection on the PC.

With conventional two-way serial communication, the Data Transmit from the PC would connect to the Data Receive on the peripheral device, and the the Data Receive from the PC would connect to the Data Transmit on the peripheral device.

However, the GM controllers do not work on a direct USB data connection, as the large USB plug on the GM USB programming cable contains a circuit board (populated with components) that interfaces the standard USB Data signals with the controller's programmable chip.

Therefore, you cannot simply connect the Transmit and Receive leads from a standard USB cable directly to the Receive and Transmit wires on the controller's plug as it will not work!

The correct GM USB programming interface lead must be used.

Alan
 

[Strato]

Thank you for your quick reply!

I have a programmable Prolific USB to Serial Comm Port (COM3) Adapter, so this should work I suppose.

The adapter has 4 wires: +5V, RXD (PC receives), TXD (PC transmits), and Ground. So am I right to connect the +5V to the Battery +, Ground to Ground, RXD to Signal Transmission and TXD to Signal Receive?

[Bikemad]

So am I right to connect the +5V to the Battery +, Ground to Ground, RXD to Signal Transmission and TXD to Signal Receive?

The +5V connection on your adapter would need to go to one of the +5V supplies on either the main harness connector or the pedelec connection, as it is used to supply the +5V which powers the controller's chip during the programming process.
It must not connect to Battery +, as the high battery voltage may kill your USB to Serial adapter if was connected while the battery was turned on.

I don't think your USB to Serial adapter is going to work with the MPIII controller, as both of the early GM USB cables used for programming the MPII and MPIII controllers show up in Device Manager as "HID-compliant devices" when they are plugged in, not COM ports. 

It's only the later MP4 and MP5 USB programming leads (used for programming the vector controllers) that show up as COM ports in Device Manager. 

Alan
 

[Strato]

I've just tried it out according to your recommended connections, but nothing happened.

The reason why I thought it should work is the following:
In July, 2013 in a german pedelec forum, someone reported having connected his MP-3 Controller successfully to his PC using his self-made USB cable. He further stated that the original GM USB cable contains a USB-2-COM adapter, based on Fry's Electronics. Is that correct?
I bought my MP-3 in August, 2013, so I thought it would be of the same generation and therefore should work with my COM port adapter.

[Bikemad]

He further stated that the original GM USB cable contains a USB-2-COM adapter, based on Fry's Electronics. Is that correct?

I have not taken any of my GM adapters apart, so I have no idea what the controller chip is. 

I have just double checked four USB programing cables on a Windows 7 PC and each of the three early GM USB cables (MPII, MPIII and External controller versions) show up in Device Manager as both "HID-compliant device" and "USB Input Device" in the "Human Interface Devices" section, whereas the later GM USB cable for the vector controllers only shows up as a "USB-SERIAL CH340 (COMxx)" entry in the "Ports (COM & LPT)" section.

Alan